Test of species richness estimators at different values of curvature parameter (C_p) using TCR data.

The curvature parameter C_p is plotted against the relative error (|S_obs - Ŝ_obs| /S_obs) of each estimator. Four patient data sets are shown: A total CD4⁺ from patient C; B total CD4⁺ from patient E; C total CD8⁺ from patient C; D total CD8⁺ from patient E. Each point represents an estimate from a subsample of data. Note the plots have different y-axis scales and the y-axes in C and D are segmented. Broadly, the accuracy of all estimators improves as C_p increases, and this increase is more pronounced for DivE. From C_p>0.1, DivE generally outperforms the existing estimators, but is prone to error at very low values of C_p., when the rarefaction curve implies a near-constant rate of species accumulation.